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Clinical, pathological, and etiologic aspects of acquired dermal melanocytosis
M Mizoguchi1, F Murakami, M Ito
1Department of Dermatology, St. Marianna University School of Medicine, Kawasaki, Japan.
Abstract:
To study the pathogenesis of acquired dermal melanocytosis (ADM), we reviewed the clinical, immunohistochemical, and ultrastructural features of 34 cases (female, 33, and male, 1) of ADM. The patients' ages at onset ranged from 8 to 51 years and averaged 26.8 +/- 12.7 years. There was a positive family history. Gray-brown macules were mostly recognized on the face. Not only active dermal melanocytes but also non-pigmented c-KIT- and TRP-2-positive immature melanocytes were detected in the dermis. Taken together those clinical and histological findings, activation of pre-existing immature melanocytes by sunlight, estrogen, and/or progesterone, and some other factors, may be the most likely mode of the development of ADM. Moreover, using cultured murine neural crest cells as a model of c-KIT-positive immature melanocytes, we confirmed that endothelin-1, which is produced and secreted by keratinocytes after UV-irradiation, affects melanocytes and accelerated melanogenesis.
Insights
Acquired dermal melanocytosis (ADM) may develop from the activation of immature melanocytes in the dermis. Factors like UV radiation stimulate melanogenesis, potentially causing ADM.
Area of Science:
- Dermatology
- Pathogenesis Research
- Cell Biology
Background:
- Acquired dermal melanocytosis (ADM) is a condition characterized by gray-brown macules, primarily on the face.
- The exact pathogenesis of ADM remains incompletely understood, necessitating further investigation into melanocyte behavior.
- Previous studies have indicated a potential role for melanocytes in the dermal layer, but their activation mechanisms require clarification.
Purpose of the Study:
- To elucidate the pathogenesis of acquired dermal melanocytosis (ADM).
- To investigate the characteristics of melanocytes present in ADM lesions.
- To identify potential triggers and cellular mechanisms involved in ADM development.
Main Methods:
- Review of clinical, immunohistochemical, and ultrastructural features in 34 ADM cases.
- Histological examination to identify active and immature melanocytes in dermal tissue.
- In vitro study using cultured murine neural crest cells to model melanocyte response.
Main Results:
- ADM cases showed both active dermal melanocytes and immature, non-pigmented melanocytes (c-KIT- and TRP-2 positive) in the dermis.
- A positive family history was noted in some patients.
- Cultured murine neural crest cells demonstrated that endothelin-1 accelerates melanogenesis.
- Endothelin-1, secreted by keratinocytes after UV exposure, impacts melanocytes.
Conclusions:
- The development of ADM likely involves the activation of pre-existing immature melanocytes in the dermis.
- Sunlight, estrogen, progesterone, and other factors may trigger melanocyte activation and contribute to ADM.
- UV-induced endothelin-1 production by keratinocytes plays a role in accelerating melanogenesis, supporting its involvement in ADM pathogenesis.